This invention relates to Schiff reagents and, more particularly, to a Schiff reagent which is stable at room temperature.
The Schiff reagent, a well-known reagent, is a complex organic molecule which is specific for aldehydes generated in biological specimens.
The Schiff reagent was first formulated by the German chemist Hugo Schiff as a qualitative test for aldehydes in 1865; rosanilin, a magenta colored dye, was converted to a colorless (leuko) reagent by the addition of sulfur dioxide to an aqueous solution. The reagent became recolorized by the addition of compounds containing the aldehyde functional group.
The first biological application of the Schiff reagent was in 1924 by Feulgen and is known by his name. Feulgen used the reagent to detect aldehydes generated by acid hydrolysis of deoxyribose sugar of deoxyriboneucleic acid (DNA).
The Schiff reagent has always been known as an unstable reagent. As described in 1960 [Kasten, F. H. (1960): The Chemistry of Schiff Reagent, Intl. Rev. Cytol. 10:1-100.], the stability of the Schiff reagent ranges "from several hours to six months or longer, depending on the ingredients and the method of storing". The greatest longevity described was 13 months when the reagent was stored in a brown stoppered bottle in the refrigerator.
The stability of the reagent is directly affected by the loss (by evaporation) of SO.sub.2 from the reagent. Where the loss of SO.sub.2 is great and at a fast rate, the stability of the reagent decreases until it deteriorates and is of no use.
Accordingly, various methods have been employed to prevent the loss of SO.sub.2. Two obvious methods were by storing the reagent in a stoppered bottle and at a low temperature. Evaporation of the SO.sub.2 was also minimized by covering the surface of the reagent with xylene or mineral oil.
All of these methods have assisted in the control of the loss of SO.sub.2. However there is still a need to maintain the level of SO.sub.2 in the reagent and thus the stability of the reagent for a substantial period of time.
The present invention, as described below, satisfies this need by providing a sensitive reagent which is stable for a substantial period of time.